Nonlinear Control Design of MFCI for PMSG WECS with Low Voltage Ride-Through Enhancement

The large penetration of wind energy conversion systems (WECS) into the grid requires more grid support functions such as power smoothing and low-voltage ride-through (LVRT) capability. In this paper, a new control scheme is proposed for the LVRT enhancement of a multilevel flying capacitor inverter-based permanent magnet synchronous generator (PMSG) wind turbine. The proposed method uses flying capacitors as storage units to smooth out the wind power fluctuations and also store the generated power for short-term grid disturbance. Furthermore, a nonlinear controller is designed for capacitor voltage balancing, power factor correction, and dc-link voltage regulation. The overall control scheme is verified by the numerical simulations. The WEC system behavior is evaluated during different grid operation modes.